The water resistance of the coating film can be measured according to the national standard GB/T1733-93 "Determination of Water Resistance of Paint Films". This standard specifies the test methods for the water resistance of paint films, including two methods: the water immersion test method and the boiling water test method. After the specified test time is reached, the water resistance performance is expressed by the change of the surface of the paint film.
(1) Materials and equipment
① Bottom plate: The bottom plate should be flat, without distortion, and there should be no visible lines and wrinkles on the surface of the board. Unless otherwise specified, the bottom plate shall be 120rnx25mm (0.2~0.3)mrn tinplate.
②Distilled water or deionized water: meet the requirements of the third-grade water in GB6682.
③Glass sink
(2) Treatment and coating of the bottom plate
Unless otherwise specified, prepare the paint film on three tinplate plates according to the provisions of GB1727.
(3) Coating on the edge of the test panel
Unless otherwise specified, the edge of the test panel should be sealed with a mixture of paraffin wax and rosin at a ratio of 1:1, and the width of the edge should be 2~3mm.
(4) Test procedure
① Method A: water immersion test method
Immersion of the test panel: Add distilled or deionized water into the glass tank. Unless otherwise specified, adjust the water temperature to 23°C ± 2°C and maintain this temperature throughout the test
Put three test panels into it, and soak 2/3 of the length of each test panel in water.
b. Inspection of the test plate: After the immersion time specified in the product standard is over, take the test plate out of the tank, blot it dry with paper, and inspect the test plate visually immediately or after adjusting the time state specified in the product standard , and record the phenomenon of loss of gloss, discoloration, blistering, wrinkling, shedding, rusting and other phenomena of the coating film of the test panel and the recovery time.
At least two test panels among the three test panels shall meet the requirements specified in the product standard and be considered qualified.
②Method B: boiling water test method
Immersion of the test plate: Add distilled water or deionized water into the glass tank. Unless otherwise specified, keep the water at a boil until the end of the test.
Put three test panels into it, and soak 2/3 of the length of each test panel in sub-water.
b. Inspection of the test panel: inspect and evaluate the test panel according to the provisions of Law A.
